There were probably growing conditions that the plant was subjected to, prior to being shipped to be on display with all flowers blooming for some customer to buy it.

You can help a little by trimming the plant or deadheading the blooms. That way, the plant will grow bushier with more branches, and that means more buds, and that means the chance that more of them are blooming all at the same time.

When you trim the plant, you can try your hand at rooting the cuttings and get more geranium plants.